Now this is a remarkable find.
It is also probably the only falling rock sign living in The Netherlands.

The caption in[s]tortingsgevaar makes clear that this is not a sign warning about falling rocks, but rather about the sand cliff — about 50cm high— which may collapse. You can never be too careful, someone must have thought.

The design is very close to the German Falling Rock sign with five stones. The cliff face is different though.